I love the idea! We could ask the caterer to offer, say 10% (?) discount for everyone who pays in DASH, and then we just compensate it afterwards. 10% of $10 buy is only $1 so that's almost like nothing. However, it's difficult to estimate the number of buys in DASH well in advance...it also depends on whether people can somehow buy Dash on site. We could ask 1 - 1.5 DASH extra, which means we would be able to cover around 300-500 $10 buys (we also need to take InstantSend fee out of the price) and in case there are only few buys, we will increase our giveaway in the end or after the events on social media?
I think this idea will draw extra attention on Dash and we may see people who didn't get DASH via giveaway, but are still interested in (since they can get discount!) and want to buy DASH. If they could get DASH immediately and use it right for payment, then we will win another person on our side, but I'm afraid they lose interest when they hear about the rather complicated and time consuming way of buying it.
We will think about it, but if somebody has an idea how could we help them to obtain (low amounts) DASH quickly, that would be way too awesome!